2022 U.S. Joint Research Target on Intrinsically Non-ELMing Enhanced Confinement Regimes
2022 U.S. Joint Research Target on Intrinsically Non-ELMing Enhanced Confinement Regimes
Simulation
Magnetic Confinement

2022 U.S. Joint Research Target on Intrinsically Non-ELMing Enhanced Confinement Regimes

The 2022 U. S. Joint Research Target focused the efforts of 45 researchers in 5 working groups to carry out extensive simulations and new experiments to advance stable, high performance confinement regimes without edge localized mode transients.

Principal Investigator
Darin Ernst
Research Scientist
Team
An older white woman with short white hair and frame-less glasses smiles broadly
Amanda Hubbard
Amanda Hubbard
01
Importance of research

The 2022 U. S. Joint Research Target focused the efforts of 45 researchers in 5 working groups to carry out extensive simulations and new experiments to advance stable, high performance confinement regimes without edge localized mode transients. These are advanced operating regimes featuring, for example, favorable confinement scalings, reduced divertor heat loads, and promising compatibility with future burning plasmas. A dedicated DIII-D experimental thrust, “Develop Non-ELMing High Performance Scenarios” was co-led by D. Ernst (MIT) and Xi Chen (GA) in FY22-23, with 13 experiments allocated over 9 run-days. The experiments produced the highest power I-Modes yet obtained, and extended Wide Pedestal Quiescent H-Mode to higher power and lower safety factor, demonstrated methods to control impurities including tungsten in WPQH-Mode, and obtained WPQH-mode in hydrogen plasmas with greatly reduced impurity content, while showing no isotope mass effect on confinement. The QH/WPQH-Mode experiments also demonstrated doubling of the divertor heat flux profile width by using actuators to double the amplitude of turbulence in the pedestal. These results were quantitatively matched by supercomputer simulations using the XGC gyrokinetic particle code. An intensive simulation effort using a variety of codes identified instabilities and transport mechanisms in the edge pedestal underlying energy, particle, and impurity transport.

Importance of Research

High energy confinement is required to obtain high plasma pressure, while fusion power increases with the square of plasma pressure. This high confinement (“H-Mode” operation) is produced through an edge transport barrier, which causes the pressure to increase until it becomes unstable to peeling-ballooning modes, causing a sudden ELM (Edge Localized Mode) crash. The ELMs would produce disastrous material erosion in future machines. Non-ELMing regimes avoid ELMs by limiting the edge transport barrier through turbulent transport so it does not reach the stability limit. Several of these regimes (QH-Mode, Wide Pedestal QH-Mode, I-Mode, EDA H-Mode, Enhanced Pedestal H-Mode, etc.) have been under development as alternative operating modes for ITER and other future machines, both to increase performance as well as to avoid ELMs. Scaling arguments suggest that turbulence may limit pedestals naturally in future high magnetic field machines.

02
Methods

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03
Milestones
Papers

Ernst, Darin; Bortolon, Alessandro; Chen, Xi; King, Jacob; Nelson, Andrew O.; Battaglia, Devon; Hubbard, Amanda; Final Technical Report for the 2022 Magnetic Fusion Energy Joint Research Target: Intrinsically Non-ELMing Enhanced Confinement Regimes, Prepared for the Fusion Energy Sciences Program, DOE Office of Science, September 30, 2022 (163 pp). General Atomics Report GA-C29760. To become available from https://science.osti.gov/fes/community-resources. D. R. Ernst, White Paper #65: Developing Non-ELMing Enhanced Confinement Regimes for ITER, 2022 US ITER Research Needs Workshop. D. R. Ernst et al., “Results of the 2022 U.S. Joint Research Target on Intrinsically Non-ELMing Enhanced Confinement Regimes,” Invited Paper BI02.6, 65th Annual Meeting of the APS Division of Plasma Physics, Denver, Colorado, October 30-November 3, 2023. D. R. Ernst et al., “Recent Experiments and Simulations to Develop Intrinsically Non-ELMing Enhanced Confinement Regimes,” 2023 European Physical Society Plasma Physics Conference, Bordeaux, France, July 3-7, 2023. (overview of 2022 Joint Research Target) D. R. Ernst et al., “New Developments in Wide Pedestal QH-Mode Transport from Core to SOL,” Plenary Talk, 2022 U.S.-E.U. Transport Task Force Meeting, Santa Rosa, California, April 5-8, 2022. D. R. Ernst et al., “FY22 JRT Progress, Plans and Discussion: Intrinsically ELM-stable Enhanced Confinement Regimes,” 2022 Edge Coordinating Committee Meeting, Santa Rosa, California, April 6, 2022.

04
Funding acknowledgement

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FC02-04ER54698, DE-SC0014264, DE-SC0018429 (and Subaward No. UTA18- 000276), DE-FC02-99ER54512, DE-AC02-09CH11466, DE-AC52-07NA27344, DE-FG02-08ER54999, DE-SC0019004, DE-FG02-97ER54415, DE-AC02-05CH11231, DE-SC0022270, DE-SC0019352, and DE-NA0003525.